Ford, say, developed large hybrid at last (6)
I believe the answer is:
gerald
'ford' is the definition.
(I've seen this in another clue)
'developed large hybrid at last' is the wordplay.
'developed' indicates an anagram.
'at last' suggests the final letters.
The last letter of 'hybrid' is 'd'.
'large' with letters rearranged gives 'geral'.
'geral'+'d'='GERALD'
'say' acts as a link.
(Other definitions for gerald that I've seen before include "- - Ford, ex-US president" , "- Moore, accompanist" .)